When you are in want of some Guids, Internal Fieldnames or ContenttypeIDs during the development... you don't have to look that far. I just realized that the info is available in the URL.
So when you need a List Guid, just navigate to the list settings page and copy the Guid after the "List=" string. Be aware of that the GUID is URL encoded. For that reason you have to decode the Guid or just remove the special characters and add braces.
For a ContenttypeID, navigate to the contenttype in the site contenttype gallery and copy the ID after the "ctype=" string out of the URL.
For an internal Fieldname, navigate to the site column page for a particular column and copy the fieldname after the "field=" string out of the URL.